Wednesday, April 23, 2014

Typex cipher machines for the Polish Foreign Ministry

In 1926, the British Government set up an
Inter-Departmental Cypher Committee to investigate the possibility of replacing
the codebooks then used by the armed forces, the Foreign Office, the Colonial
Office and the India Office with a cipher machine. It was understood that a
cipher machine would be inherently more secure and much faster to use in
encoding and decoding messages. Despite spending a considerable amount of money
and evaluating various models by 1933 the committee had failed to find a
suitable machine. Yet the need for such a device continued to exist and the
Royal Air Force decided to independently fund such a project. The person in
charge of their programme was Wing Commander Lywood, a member of their Signals
Division. Lywood decided to focus on modifying an existing cipher machine and
the one chosen was the commercially successful Enigma. Two more
rotor positions were added in the scrambler unit and the machine was modified
so that it could automatically print the enciphered text. This was done so
these machines could be used in the DTN-Defence Teleprinter Network.

The new machine was called Typex (originally
RAF Enigma with TypeX attachments). In terms of security it was similar to a
commercial Enigma but had the additional security measure of multiple notches
per rotor. This meant that during encipherment the rotors moved more often than
in the standard Enigma machines.

During WWII
the Polish foreign ministry relied on enciphered codebooks for its secret
communications. Perhaps they were interested in Typex because they considered
their own systems insecure. Whatever the reason it doesn’t seem like they were
given any machines since the report says ‘the
supply position in respect of Type X is such that it is probably impossible to
meet their requirements for the time being’

It is
interesting to note that the same report says ‘provided the Type X machines supplied were not fitted with Plugboard
and provided also we wired for them and supplied the necessary drums, the advantages to be gained by meeting
their request would outweigh the disadvantages’.